LED Low Refractive Index Layers Reduce Guided Light
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Solution Overview
Problem
Conventional methods for light extraction from light-emitting diodes (LEDs) fail to effectively reduce guided light, which limits the efficiency of light extraction due to total internal reflection and additional guiding effects within the active region, leading to suboptimal performance.
Innovation Solution
Incorporating low refractive index material layers within or around the active region of LEDs to reduce light guiding effects, which can be achieved by using low refractive index layers made of materials like AlGaN, AlInN, or AlInGaN, strategically positioned to minimize guided light propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional light extraction methods (shaping LED or roughening surfaces) are used, then light extraction is improved, but guided light cannot be effectively reduced
Solution Approach 1:
The patent changes the refractive index parameter by introducing low refractive index material layers (such as AlGaN, AlInN, or AlInGaN) with refractive indices significantly lower than the active region material. These layers are strategically positioned within or around the active region to modify the optical parameters and reduce guided light propagation, thereby resolving the contradiction between improving light extraction and reducing guided light effects.
Solution Approach 2:
The patent employs composite material structures by combining the active region material with low refractive index material layers to form a multi-layered structure. This composite approach allows the system to simultaneously achieve effective light extraction and guided light reduction by leveraging the complementary optical properties of different materials, where the low refractive index layers suppress guided modes while the active region maintains light emission.
2Reliability
If low refractive index material layers are introduced, then guided light is reduced, but device structure becomes more complex
Solution Approach 1:
The low refractive index material layers are designed to perform multiple functions simultaneously: they reduce guided light propagation by modifying optical parameters, serve as electron blocking layers to improve carrier confinement, and can function as part of the overall device architecture. This multi-functionality reduces the need for separate dedicated components, thereby mitigating the increase in device complexity while achieving guided light reduction.
3Reliability
If low refractive index layers are positioned within one optical wavelength of the active region, then light guiding is substantially reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by positioning low refractive index material layers at specific locations within one optical wavelength of the active region where guided light modes are most prominent. Rather than uniformly distributing layers throughout the device, the low refractive index materials are strategically placed in regions where they most effectively disrupt guided light propagation, thereby achieving high reliability in guided light reduction with manageable manufacturing precision requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of low refractive index material layers significantly reduces the fraction of guided light in the active region, enhancing light extraction efficiency and improving the overall performance of LEDs by minimizing light loss through absorption-emission cycles.
Implementation Method 1
a fraction of the light generated by the LED internally reflects from the interfaces with the outside medium (either air or an encapsulant) due to total internal reflection
Implementation Method 2
LEDs are made of a high refractive index semiconductor material... low refractive index material layers... configured to substantially reduce light guiding
Data Source
AI summary
A light-emitting diode (LED) for emitting emitted light having a particular wavelength, said LED comprising: (a) at least one n-doped layer; (b) at least one p-doped layer; (c) an active region comprising at least one layer of light-emitting material disposed between said at least one n-doped layer and said at least one p-doped layer, said active region having an average refractive index, calculated by averaging the LED's refractive index across the thickness of the active region; and (d) at least one low refractive index layer disposed within said particular wavelength of said active region, said at least one low refractive index layer having a refractive index below said average refractive index and a thickness sufficient to limit light being emitted into a guided mode of said active region to no more than 10% of said emitted light.